Load responsive breake release



NOV- 24, 1964 G. E. HEBERLEIN LOAD RESPONSIVE BRAKE RELEASE Filed Dec. 24, 1962 United StatesPatent O 3,158,233 LOAD RESPONSIVE BRAKE RELEASE Gustave E. Heberlein, Bryn Mawr, Pa., asslgnor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 24, 1962, Ser. No. 246,723 7 Claims. (Cl. 18S- 171) This invention relates lto a novel brake release structure, and more specifically relates to a novel brake release structure which can be used in hoist motor systems wherein an initial upward movement of the hoist load 1s required prior to release of the brake.

Brakes for use with hoists are commonly s et by a spring force which is released by the energizatlon of a magnet. arrangement, and could be applied, for example, Vwith hoists of the type shown in copending application Serial No. 212,335, tiled July 25, 1962, entitled A.C. Ho1st Control System in the name of Ronald I. Bohn and assigned to the assignee of the instant invent1on.

Generally, in such hoist control schemes, the brake release coil and hoist motor are energized simultaneously. However, the torque developed by the motor may be 1nsuicient at the first hoist position of the hoist controller to overcome the weight of the load, the result being that the load will move down instead of up.

The principle of the present invention is to provide a lost motion connection between the brake release control structure and the hoist motor, wherein brake release .is possible only after the Vlost motion has been absorbed during the initiation of a hoisting operation. Thus, horsting operation cannot be initiated by the operator unless he is at a controller position which provides suficient torque `for lifting the load.

In a particular embodiment of the invention, the lost motion connection cooperates with an auxiliary contact which is connected in series with the brake release magnet. Thus, the brake release magnet cannot be energized until the hoist motor has moved the load through a relatively small lost motion distance, -thus assuring that upward motion can be initiated before the brake is released.

Accordingly, a primary object of this invention is to prevent release of a brake in a hoist control system until sufficient torque is available for assuring the upward motion of a load.

Another object of this invention is to remove, from the discretion of the operator,fthe determination of a controller position sufficient to move a load upwardly before release of a hoist brake.

These and other objects of this invention will become apparent from the following description when taken in connection with the accompanying drawing which illustrates a side plan view of a portion of the brake release structure of a hoist constructed in accordance with the invention.

Referring to the drawing, I have illustrated therein the output 4shaft 10 of a motor hoist which is, for example, connected to a hoist rope 11. The hoist rope 11 can go over an overhead series of pulleys (not shown), and then come downwardly to terminate in a lifting hook. As indicated by the arrows in the figure, the motor hoisting torque is in a clockwise direction, while load torque or the torque exerted on the motor by a load will be counterclockwise. v

In accordance with standard techniques, a brake drum 12 of any standard `type and which can have any desired length is secured to the output shaft of the hoist motor. The drum 12 then cooperates with an appropriate brake shoe 13 which again can be of -any standard type, and is This is a common and Well known fail-safe .o 3,158,233 Patented Nov. 24, 1964 carried from a brake cradle 14 by means of a pin 15 in the usual manner. The cradle 14 is then pivotally mounted to a support structure 16' at pivot 17.

` In accordance with the present invention, cradle 14 receives pin in a lost motion slot 16 which is elongated in a direction which is tangential to drum 12.

A relatively strong spring 18 is then provided tothe right of pivot 17 to normally bias shoe 13 into engagement with drum 12. In order to release drum 12, the cradle 14 carries a magnetic larmature 19 which is in spaced relationship with respect to a magnet coil 20. The magnet coil 20 is provided with two energizing leads 21 and 22 which are connectable to any appropriate power source such as the terminals 23'and 24 of a D C. source. The D.C. source is then connected to magnet coil 20 by the operation of a two-position switch 25.

When it is desired to lower a load secured to rope 11,I the switch 25 closesat terminal 26 labeled L (for lower) so that the D.C. source is directly connected to magnet coil 20. The energization of magnet coil 20 attracts armature 19 and compresses spring 18 so that the cradle 14 rotates in a clockwise direction around pivot 17. This releases shoe 13 from drum 12 so that the lowering oper-ation can proceed. q

In accordance with the invention, and where the load is to be hoisted rather lthan lowered, the control switch25 is connected to terminal 27 which is labeled H `(for hoist). y

An auxiliary switch means which includes stationary contacts 28 and 29 which cooperate with a movable bridge;

contact is then carried from cradle 14. Contacts 28 and 29 are connected in ser-ies with the D.C. source terminal 27 and the magnet coil 20. Thus, in order for the magnet coil 20 to be energized, bridge 30 must be moved downwardly and into engagement with contacts 28 and 29. The bridge 30 is carried on a lever 31 which is pivotally mounted at pivot 32-wherein the switch structure is all carried from cradle 14. The left-hand end of lever 31 is held in engagement with the top of pivot pin 15 by means of a spring 33.

In operation, -it will now be understood that the switch arm 30 will move downwardly with respect to contacts 28 and 29 only when the pin 15 moves to the bottom of slot 16. Thus, when the operator operates the controller Vfor a hoisting operation which will close switch 25 to terminal 27 and apply appropriate voltages to the motor for hoisting torque, if the torque is insuiiicient to cause a hoisting operation, pin 15 will not move downwardly in lost motion slot 16 so that a circuit is not completed through magnet Vcoil 20. Thus, the brake is not released.

When, however, the operator energizes the appropriate controller position on his controller so that the motor hoisting torque is suflicient to begin to lift the load, the motor shaft 10,I drum 12 and brake 13 will'all begin to rotate about themotor shaft axis so that pin 15 will move to the bottom of lost motion slot 16. This will cause bridging contact 30 to engage contacts 28 and 29 whereby an electrical circuit is completed to magnet coil 20 which causes the cradle 14 to rotate about pivot 17 to release the brake shoe 13.

Accordingly, it will be seen that a brake release structure is provided which is operable only when sufiicient torque is applied to the motor to insure that a hoisting operation will follow the release of the brake.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of this invention be limited not by the specific disclosure herein but only by the appended claims.

What is claimed is: t

L'A load responsive brake comprising a brake drum, a brake shoe, support means for said brake shoe, a brake engaging means, a brake release means, a motion responsive switch means, and a lost mot-ion connection means; said lostmotion connection means being connected to said brake shoe by said lost motion connection means, said support means being movable with respect to said brake drum between a brake engaging and a brake disengaging position; said brake engaging means compris- -ing a biasing spring connected to said `support means for normally biasing said brake shoe into engagement with said brake drum; saidbrake release means comprising magnet coil means energizable for-moving saidrsupport means toward said brake disengaging position against the biasing force of said biasing' spring; said lost motion connection means permitting rotation of said brake drum for a predetermined distance'while `saidbralre shoe engages said brake drum; said motion responsive switch means being operatively connected to said lost motion connection means; said switch means being closed when both said brake drum and said brake shoe rotate through said predetermined distance; andan energizing circuit for energizing said magnet coil; saidrenergizing circuit ben-g connected in series with said switch means. Y

2. The device substantially .as set forth in claim 1 Wherein'saidrlost motion connection means includes a pin secured to one of said brake shoe'or support means and an elongated slot in the other of said brake shoe or support means; s'aid pin extending through said slot.

3; The device substantially as. lset forth in claim 2 Whereinsaid slot is elongated in a direction whichv is parallel to a line ltangent to said brake drum.

4. A brake cont-rol structure for `a'lioist to prevent release of a brake before sueient lifting torque is provided by said hoist; said hoist having -a motor; the shaft of said motor being operatively connected to a brake drum; said bnake controls'tructure including a brake shoe, support means for said brake shoe, a' brake engaging means, a brake'release means, a motion responsive switch means, and a lost motion connection means;-said support means being connected to lsaid brake shoe by said lost motion connection means, said support means being movable with respect lto Ysaid brake drumv between a b-nake Vengaging and a brake disengaging position; said brake engaging means comprising a biasing spring connected to said -support means for normally biasing said brake :shoe into en-` gagementwith said brake drum; saidbrake release means comprising -magnet coil` means energizable for moving said support means towardsaid brake disengaging posi'- tion against the biasing force of said biasing sprng; said lost motion engaging means permitting rotation'of said brake drum for a predetermined distance while said Vbrake shoe" engages said'brake drum; `said motion responsive switch means being operatively' connected to said lost motion connectionmcans; said switch means being closed when both said brake drumV and said brake shoe rotate through said predetermineddistanceyand an energizing circuit for energizing said magnet coil; said energizing circuit being connected in serieswith said switch means whereby said brake shoe is released only when there is initial moton of said brake drum to assure sufficient lifting torque for said hoist.

5. In a brake; a brake drum having an engaged and disengaged position with respect to said brake drum, a brake shoe, a pivotally mounted cradle for supporting said brake shoe, and electricaily energizable means for rotating said cradle to move said brake shoe from its said engaged position to its said disengaged position; said brake shoe being connected to said cradle by a lost motion connection; a switching means; said switching means having an operating member connected to said lost motion connection; said switching means being moved to a closed position responsive to relative movement between said brake shoe yand cradle in said lost motion connection; and energizing means for energizing said electrically energizable means; said energizing means being connected in` series with said switching means.

6. In a brake; a brake drum having an engaged and disengaged position with respect to said brake drum, a

brake'shoe, a'pivotally mounted cradle for supporting f said brake shoe, and electrically energizable meansfor rotating'said cradle to move said brake Yshoe from its said engaged position to its saidvr disengaged4 position; said brake shoe being connectedto said cradle by a lost motionl connection; a switching means; said 'switching means Ihaving lan operating memberconnected to said 10st motion connection; said switching means being moved to a closed position responsive to'relative movement bef tween said brake shoe and cradle in saidrlost motion connection; 'and energizingV means for energizing said'eleo-V trically energizablemeans; saidenergizing means being connected in series with said switching means; saidvlost motion connection including a pin secured to one of said brake shoe or support means and anelongated slot in the other of'saidgbrake shoe or support means; said pin extending throughsaid slot.

, 7. Ina brake; a brake drum having an engaged and disengagedV positionwith respecttos'aid br'akedrum'a brake shoe, a pivotally mounted cradle for supporting said brake shoe, and ,electrically energizable means for rotating said cradle to move said brake shoe from its said engaged position to its said disengaged positiomsaid brake' shoe being connected to said cradle bya lost motion connection; a switching means; said switching means having an operat-V ing'member connected to said` lost motion connection; said switchingrmeansV being moved to a closed position responsive to relative movement between vsaid brake shoe andV cradle in said rlost motion connection; and energizing fmeans for energizing said` electrically energizable means; said energizingmeans being connected in series with said switching means; said lost motion` connection includingra pin secured to one Yofsaid brake shoe .or support means and an elongatedslotwin the other of said i brake shoe or Vsupport means; saidrpin extending/through said slot; said slot-being placed in saidcradle and being elongated in a direction which is parallel to a line tangent to saidbrake drum.V 1`

No references cited. 

1. A LOAD RESPONSIVE BRAKE COMPRISING A BRAKE DRUM, A BRAKE SHOE, SUPPORT MEANS FOR SAID BRAKE SHOE, A BRAKE ENGAGING MEANS, A BRAKE RELEASE MEANS, A MOTION RESPONSIVE SWITCH MEANS, AND A LOST MOTION CONNECTION MEANS; SAID LOST MOTION CONNECTION MEANS BEING CONNECTED TO SAID BRAKE SHOE BY SAID LOST MOTION CONNECTION MEANS, SAID SUPPORT MEANS BEING MOVABLE WITH RESPECT TO SAID BRAKE DRUM BETWEEN A BRAKE ENGAGING AND A BRAKE DISENGAGING POSITION; SAID BRAKE ENGAGING MEANS COMPRISING A BIASING SPRING CONNECTED TO SAID SUPPORT MEANS FOR NORMALLY BIASING SAID BRAKE SHOE INTO ENGAGEMENT WITH SAID BRAKE DRUM; SAID BRAKE RELEASE MEANS COMPRISING MAGNET COIL MEANS ENERGIZABLE FOR MOVING SAID SUPPORT MEANS TOWARD SAID BRAKE DISENGAGING POSITION AGAINST THE BIASING FORCE OF SAID BIASING SPRING; SAID LOST MOTION CONNECTION MEANS PERMITTING ROTATION OF SAID BRAKE DRUM FOR A PREDETERMINED DISTANCE WHILE SAID BRAKE SHOE ENGAGES SAID BRAKE DRUM; SAID MOTION RESPONSIVE SWITCH MEANS BEING OPERATIVELY CONNECTED TO SAID LOST MOTION CONNECTION MEANS; SAID SWITCH MEANS BEING CLOSED WHEN BOTH SAID BRAKE DRUM AND SAID BRAKE SHOE ROTATE THROUGH SAID PREDETERMINED DISTANCE; AND AN ENERGIZING CIRCUIT FOR ENERGIZING SAID MAGNET COIL; SAID ENERGIZING CIRCUIT BEING CONNECTED IN SERIES WITH SAID SWITCH MEANS. 